Officials are probing how a 51-year-old highway bridge came to collapse in the Italian port city of Genoa yesterday, killing at least 26 people and injuring 16 others as it sent dozens of vehicles tumbling into a heap of concrete and twisted steel.

'No' campaign's new TV ad rated too explicit

Explicit content in the 'No' campaign's new TV advert has resulted in an 'MA' rating and a restricted broadcast timeslot.

The 30-second ad by the Coalition for Marriage for the same-sex marriage survey has been listed as not suitable for children, reports the ABC.

It features two women discussing their concerns for children being taught homosexual intercourse and gender issues while cards claiming to quote parts of the controversial 'Safe Schools' programs appear on the screen.

Part of the text includes the words: “Penis-in-vagina sex is not the only sex and certainly not the ultimate sex.”

Safe Schools founder Roz Ward also features in the ad, along with elements of the pro-LGBT campaign'S ‘OMG I’m Trans and OMG I’m Queer’ materials.

Free TV, the organisation that classifies adverts and regulates their viewing times defended the move.

"This ad was given an MA rating because of references to sexual activities," acting chief executive of Free TV Australia Pamela Longstaff said.